Method and device for calibrating and updating a power model

ABSTRACT

A method and device for calibrating a power model for a multi-state device. The device includes a processor and a computer readable medium containing instructions to instruct the processor to perform the method. The method includes receiving a device state log comprising a time-based representation of multi-state device states for a first period of time and a power trace comprising a time-based representation of power consumed by the multi-state device for the first period of time; eroding the device state log to reduce potential noise present at state transitions within the device state log, thereby producing an eroded device state log; determining energy consumption for each state transition in the eroded power state log; creating an updated power model for the multi-state device based upon the eroded power state log; and storing the updated power model in a non-transitory computer readable medium operably connected to the multi-state device.

BACKGROUND

The present disclosure relates to power modeling for a device. Morespecifically, the present disclosure relates to calibrating and updatinga device's power model.

Energy consumption reporting and control for a device, such as an officedevice, is becoming more interesting to consumers. As electricitybecomes more expensive, and consumers strive to become moreenvironmentally conscious, accurate power consumption and modeling isbecoming more important.

Many office devices such as printers, copiers and multifunction devices(e.g., a single device capable of scanning, printing, faxing and/orcopying) are capable of operating in one or more states. For example,when a device is not used for a given period of time, the device mayenter a “sleep” state. During a sleep state, various components in thedevice go into low power operation or are turned off completely. Oncethe device receives a request to perform a specific function, the devicemay exit the sleep state and operate as normal.

Existing techniques for energy modeling use a variety of methods, eachhaving differing accuracy and precision. Many estimate techniquesrequire some form of power model to describe the device'scharacteristics such as energy used during various states, and theenergy used by a device to transition between the states. However, eventhe most sophisticated and accurate energy consumption techniques relyon power models that ignore many factors that may contribute to energyconsumption, including accessories currently being used in combinationwith the device, potential network traffic coming to and going from thedevice, and device to device energy consumption deviation between thesame models of devices.

Manufacturers may provide a standard power model for a specific devicefor use in estimating power consumption. However, significantdifferences between devices, especially in low power state, sleep state,and idle state can exist with different device configurations andassociated accessory use, and these differences may not be accuratelyreflected in a power model for that specific device.

SUMMARY

In one general respect, the embodiments disclose a method of calibratinga power model for a multi-state device. In one embodiment, the methodincludes receiving a device state log comprising a time-basedrepresentation of multi-state device states for a first period of timeand a power trace comprising a time-based representation of powerconsumed by the multi-state device for the first period of time; erodingthe device state log to reduce potential noise present at statetransitions within the device state log, thereby producing an erodeddevice state log; determining energy consumption for each statetransition in the eroded power state log; creating an updated powermodel for the multi-state device based upon the eroded power state log;and storing the updated power model in a non-transitory computerreadable medium operably connected to the multi-state device.

In another general respect, the embodiments disclose a device forcalibrating a power model for a multi-state device. In one embodiment,the device includes a processor and a non-transitory computer readablemedium operably connected to the processor. The computer readable mediumcontaining a set of instructions configured to instruct the processor toreceive a device state log comprising a time-based representation ofmulti-state device states for a first period of time and a power tracecomprising a time-based representation of power consumed by themulti-state device for the first period of time; erode the device statelog to eliminate potential noise present at state transitions within thedevice state log, thereby producing an eroded device state log;determine energy consumption for each state transition in the erodedpower state log; create an updated power model for the multi-statedevice based upon the eroded power state log; and store the updatedpower model in at least the non-transitory computer readable medium.

In another general respect, the embodiments disclose a method ofcalibrating a power model for a multifunction printing device. Themethod includes receiving a device state log comprising a time-basedrepresentation of multifunction print device states for a first periodof time and a power trace comprising a time-based representation ofpower consumed by the multifunction print device for the first period oftime, wherein each of the device states represents a specific functionthe multifunction print device is configured to perform; eroding thedevice state log to reduce potential noise present at state transitionswithin the device state log, thereby producing an eroded device statelog; determining energy consumption for each state transition in theeroded power state log; creating an updated power model for themultifunction print device based upon the eroded power state log; andstoring the updated power model in a non-transitory computer readablemedium operably connected to the multifunction print device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a device state log for a first period of time accordingto an embodiment.

FIG. 2 depicts a power trace for the device state log as shown in FIG. 1according to an embodiment.

FIG. 3 depicts a sample flow diagram of a method for calibrating andupdating a device's power model according to an embodiment.

FIG. 4a depicts an eroded device state log according to an embodiment.

FIG. 4b depicts a smoothed power trace according to an embodiment.

FIG. 5 depicts various embodiments of a computing device forimplementing the various methods and processes described herein.

DETAILED DESCRIPTION

This disclosure is not limited to the particular systems, devices andmethods described, as these may vary. The terminology used in thedescription is for the purpose of describing the particular versions orembodiments only, and is not intended to limit the scope.

As used in this document, the singular forms “a,” “an,” and “the”include plural references unless the context clearly dictates otherwise.Unless defined otherwise, all technical and scientific terms used hereinhave the same meanings as commonly understood by one of ordinary skillin the art. Nothing in this disclosure is to be construed as anadmission that the embodiments described in this disclosure are notentitled to antedate such disclosure by virtue of prior invention. Asused in this document, the term “comprising” means “including, but notlimited to.”

As used herein, a “device” refers to an electronic device configured toperform one or more specific functions. Each device has an associatedpower model that defines the device's power consumption during certainstates as well as the device's power consumption during transitionsbetween certain states.

A “power model” is an estimated representation of power usage for aspecific device. If the device is a multifunction device configured tooperate in multiple states, the power model includes power consumptionlevels for each of the multiple states as well as power consumptioninformation for transitioning between from one state to another. A powermodel may be provided by the manufacturer of a device, or determined bymeasuring the power consumption of the device as it operates.

A “printing device” is an electronic device that is capable of receivingcommands, and/or printing text characters and/or images on a substrate,and/or scanning images. Printing devices may include, but are notlimited to, network printers, production printers, copiers and otherdevices using ink or toner, and scanners. A printing device may alsoperform a combination of functions such as printing and scanning, inwhich case such a device may be considered a multifunction device.

A “computing device” refers to a device that processes data in order toperform one or more functions. A computing device may include anyprocessor-based device such as, for example, a server, a personalcomputer, a personal digital assistant, a web-enabled phone, a smartterminal, a dumb terminal and/or other electronic device capable ofcommunicating in a networked environment. A computing device mayinterpret and execute instructions.

The present disclosure is directed to a method for calibrating a powermodel of a device, both at manufacture of the device and in field oncethe device has been installed and is operational. Additionally, thepresent disclosure also include a method for updating a device's powermodel, both resident on the device and published through a standardpower management information base (MIB) associated with the device. Thecalibration method may include the use of a power meter, e.g., awireless power meter. The calibration method may utilize an MIB powerlog of a job accounting log to determine device states at specificperiods of time, and it correlates the device power state with the truepower consumption as measured by the power meter. The calibration methodmay estimate with high accuracy the device's power used for each stateas well as the related state transition costs. A new power model may becreated for the device and instated as the device's updated power model.

FIG. 1 illustrates a sample log of a device's states over a period oftime. The x-axis represents time, and the y-axis represents the variousstates for the device. As used herein, a state value refers to anumerical representation of a specific state the device is operating inat a specific time. For example, if the device is a multifunctionprinting device, the device state values may be 40: sleep, 30: lowpower, 20: idle, 21: scan, 22: print, and 23: scan and print. Forexample, as shown in FIG. 1, the device initially may be in the idlestate (20 on the y-axis) until about time 400 when it transitions to lowpower (30 on the y-axis). The device may then transition from low powerto sleep (40 on the y-axis) at approximately time 1000. At approximatelytime 1600, the device may transition from the sleep state to the idlestate. Each transition may be caused by the occurrence of any of variousevents. For example, if the device receives an indication of an incomingjob to be processed, it may transition from a sleep state to an idlestate. Alternatively, a user may have pushed a button or otherwiseinteracted with a user interface on the device, causing the device totransition to the idle state.

As shown in FIG. 1, between approximately time 1600 and 4600, the devicetransitions between various active states (i.e., one of scanning,printing, and both scanning and printing) and idle. The device thentransitions back to sleep at approximately time 4600.

The state log as shown in FIG. 1 may be recorded and stored locally atthe device in a job accounting database. Additionally, or alternatively,the state log may be stored in a location that is remote from the devicesuch as memory that stores an MIB job log. By using the standard powermodel provided by the manufacturer of the device, the total powerconsumption for the device may be estimated. For example, the powermodel may indicate that the device consumes 20 watts per unit of time(as measured on the x-axis) during the sleep state and 100 watts perunit of time during the low power state. Additionally, the power modelmay indicate the power consumed by the device during transitions betweenvarious states. For example, the power model may indicate the deviceconsumes 1200 watts per unit of time to transition between the sleepstate and the idle state. However, as shown in FIG. 1, the transitionstates may occur in a relatively short period of time. For example, thetransition between idle (at time 400) and low power may be nearlyinstantaneous. However, there is a short period of time where the deviceis transitioning between the idle state and the low power state.

Variations in individual devices and operating environments may cause anindividual device to operate at power consumption levels that are notaccurately reflected in the device's manufacturer-provided power model.For example, the speed of the network to which the device is operablyattached may cause the device to receive higher amounts of data in aquicker time, causing the device to consume more power during variousstates than the same model of device connected to a slower network. Inorder to accurately measure power consumption, a power meter may be usedto measure the device's actual power consumption for a period of time.

FIG. 2 illustrates a power trace as measured by a power meter for thedevice discussed above in FIG. 1. The x-axis of FIG. 2 represents time,and the y-axis represents power consumed. Specifically, the power traceas shown in FIG. 2 corresponds in time to the state log shown in FIG. 1.For example, between time 0 and time 400, the device is in an idle state(represented by value 20 on the y-axis of FIG. 1). As shown in FIG. 2,the power consumption when the device is in the idle state fluctuatesbetween about 90 watts and 205 watts. Once the device transitions to thelow power state at approximately time 400, the power consumption levelsout at about 100 watts. When the device transitions to the sleep stateat approximately time 1000, the power consumption levels out at about 20watts.

As shown in FIG. 2 at approximately time 1600, a transition from thesleep state to the idle state requires a brief period of high powerconsumption. As before, during the idle state (between time 1600 andtime 4600), the device is mainly in the idle state, and the powerconsumption fluctuates between about 205 watts and 95 watts. However,during the periods of activity, the power consumption may spike tohigher levels. For example, at about time 200, the power may initiallyspike to about 1200 watts during the transition period, and remain atabout 800-1000 watts during the activity.

As outlined above, each device may be provided with a manufacturer powermodel. However, these power models are merely the average values for allsimilar devices, and are not calibrated for an individual device. Insome instances, the manufacturer-provided model may greatly deviate fromthe actual power model from a device, and a device that was thought tobe operating efficiently may be consuming a much higher level of powerthan indicated by the manufacturer provided power model.

FIG. 3 illustrates a sample flow diagram of a method for calibrating andupdating a device's power model based upon a correlation of a device'sstate log (e.g., as shown in FIG. 1) with an accurate power trace (e.g.,as shown in FIG. 2) to create a highly accurate and precise power modelbased upon operational parameters of the actual device.

A processing device may receive 302 a digital representation of adevice's power trace (e.g., the power trace as shown in FIG. 2) and adigital representation of the device's state log (e.g., the device statelog as shown in FIG. 1). Optionally, the processing device may align 303the power trace and the device state log. Alignment of the logs 303 maybe performed if the time base on the device being measured is differentfrom the time base of the power meter. For example, time zero mayrepresent a different real-world time on the device's timer whencompared to the power meter's timer. In this instance, the logs may bealigned 303. It should be noted, though, that alignment 303 may beoptional or avoided entirely. For example, the device's timer and powermeter's timer may be synchronized prior to device measurement so as toavoid alignment 303.

However, if the time bases are off, the power trace and the device statelog may be aligned 303 using a correction technique such as crosscorrelation. Using cross correlation provides multiple vectors ofcorrelation at different vector offsets. The maximum correlation vectormay indicate the amount of shift to be included in order to align onevector to another. By determining the amount of shift to be included,the power trace and/or device state log may be shifted accordingly.

In order to reduce any noise present at the edges of power statetransitions in the device state log, the processing device may erode 304the device state log. To erode the power state transitions, the valuesfor the transitions are reduced or eliminated in order to reduce theoverall impact of the transitions in the log. For example, to erode 304the device state log, each transition may be set to zero for theduration of time it takes to complete that transition, thus eliminatingthe power contribution of the transition state. FIG. 4a illustrates anexample of an eroded device state log based upon the device state logoriginally shown in FIG. 1. By eliminating noise associated with thetransition edges, more precise mean calculations may be acquiredregarding the actual power consumption of the device during theindividual states, as opposed to having the overall power consumptionvalues altered by the noise associated with the transitions.

Based upon the eroded device state log, the processing device maycalculate 306 mean and peak power consumption values for each powerstate. For example, for each non-zero state in the eroded device statelog (i.e., for each unit of time that the device is not in a transitionstate), the mean and peak power consumption values may be calculated 306based upon the values measured in the power trace.

To identify exact locations of transitions in the power trace, theprocessing device may smooth 308 the power trace to reduce noise. Forexample, the processing device may smooth 308 the power trace byapplying a filter based upon a moving average for the power trace, usinga sample rate of, for example, 1/sec. A moving average is a type offinite impulse response filter used to analyze a set of data points bycreating a series of averages of different subsets of the full data set.These averages may then be used to smooth out short-term fluctuations inthe data set, and to highlight longer-term trends or cycles. FIG. 4billustrates an example of a smoothed power trace based upon the powertrace originally shown in FIG. 2.

The processing device may create an initial estimate of the device'spower state trace (i.e., a combined representation of the device's statelog and power trace) by replacing 310 each state value in the erodeddevice state log with the calculated 306 mean state values.

Additionally, in order to accurately reflect power consumptionassociated with the transitions, the processing device may determine 312the energy consumption during the transitions. The power consumption maybe determine 312 by determining an area under the power trace curve ofthe smoothed 308 power trace. The area determined 312 under the powertrace curve between the start of the transition and the return of thepower trace to the calculated 306 mean for the next state (i.e., thestate being transitioned to) may represent the power consumption fromtransition start to end.

The processing device may further recalculate 314 the idle state powerconsumption for the device. For convenience, a similar erosion techniqueas used above may be used (i.e., set all transitions to zero) andrecalculating the mean power values when the device state is idle. Itshould be noted that recalculating 314 the idle power as describedherein may be an optional step that may result in a more accurateestimate. Similarly, the recalculation 314 may be applied to any powerstate. However, as a typical device spends a large amount of time in theidle state (e.g., approximately 90%), to improve efficiency and accuracythe recalculation 314 may be limited to the idle state as is shown inFIG. 3.

Based upon the determined 312 energy consumption during the transitionperiods, and the calculated 306 mean power values for each state, theprocessing device may create 316 and store an updated power model forthe device based upon the actual, measured power trace and device statelog. Once updated, the power model may be added to the MIB such thatanyone accessing the device remotely may access the power model andperform associated energy consumption estimations based upon the updatedand calibrated power model.

Depending on changes to the operation of the device, or relocation ofthe device to a new network, the calibration process may be repeated toensure that the power model associated with the device is updated andaccurate. Alternatively, the power model may be updated on a regularschedule to ensure that the device is operating appropriately, and noundiscovered errors or other problems are interfering with the operationof the device.

FIG. 5 depicts a block diagram of internal hardware that may be used tocontain or implement the various processes and systems as discussedabove. An electrical bus 500 serves as the main information highwayinterconnecting the other illustrated components of the hardware. CPU505 is the central processing unit of the system, performingcalculations and logic operations required to execute a program. Forexample, CPU 505 may perform the functions performed by the processingdevice in the above discussion of FIG. 3. CPU 505, alone or inconjunction with one or more of the other elements disclosed in FIG. 5,is a processing device, computing device or processor as such terms areused within this disclosure. Read only memory (ROM) 510 and randomaccess memory (RAM) 515 constitute examples of memory devices.

A controller 520 interfaces with one or more optional memory devices 525to the system bus 500. These memory devices 525 may include, forexample, an external or internal DVD drive, a CD ROM drive, a harddrive, flash memory, a USB drive or the like. As indicated previously,these various drives and controllers are optional devices. Additionally,the memory devices 525 may be configured to include individual files forstoring any software modules or instructions, auxiliary data, incidentdata, common files for storing groups of contingency tables and/orregression models, or one or more databases for storing the informationas discussed above.

Program instructions, software or interactive modules for performing anyof the functional steps associated with the processes as described abovemay be stored in the ROM 510 and/or the RAM 515. Optionally, the programinstructions may be stored on a tangible computer readable medium suchas a compact disk, a digital disk, flash memory, a memory card, a USBdrive, an optical disc storage medium, such as a Blu-Ray™ disc, and/orother recording medium.

An optional display interface 530 may permit information from the bus500 to be displayed on the display 535 in audio, visual, graphic oralphanumeric format. Communication with external devices may occur usingvarious communication ports 540. A communication port 540 may beattached to a communications network, such as the Internet or a localarea network.

The hardware may also include an interface 545 which allows for receiptof data from input devices such as a keyboard 550 or other input device555 such as a mouse, a joystick, a touch screen, a remote control, apointing device, a video input device and/or an audio input device.

It should be noted that multifunction office device as described aboveis provided by way of example only. The techniques and processes astaught herein may be applied to additional devices that have varyinglevels of power consumption based upon their state of operation.

Various of the above-disclosed and other features and functions, oralternatives thereof, may be combined into many other different systemsor applications. Various presently unforeseen or unanticipatedalternatives, modifications, variations or improvements therein may besubsequently made by those skilled in the art, each of which is alsointended to be encompassed by the disclosed embodiments.

What is claimed is:
 1. A method of updating a power model for amulti-state device, the method comprising: receiving, at a processingdevice, a device state log comprising a time-based representation ofstates of the multi-state device for a first period of time; measuring,by a power meter, power consumed by the multi-state device for the firstperiod of time and generating a digital representation of a power tracebased on the measured power consumption; receiving by the processingdevice, the digital representation of the power trace; eroding, by theprocessing device, the device state log wherein the eroding comprisessetting to zero a value of the representation for a duration of time ofstate transition at each state transition within the device state log,thereby producing an eroded device state log; smoothing, by theprocessing device, the power trace by applying a finite impulse responsefilter to the power trace; determining, by the processing device, energyconsumption based on an area under the smoothed power trace for thefirst period of time in the eroded device state log; creating, by theprocessing device, an updated power model for the multi-state devicebased upon the energy consumption for the first period of time in theeroded device state log; storing, by the processing device, the updatedpower model in a non-transitory computer readable medium operablyconnected to the multi-state device; and using the updated power modelto estimate energy consumption of the multi-state device.
 2. The methodof claim 1, further comprising replacing the power model of the devicewith the updated power model.
 3. The method of claim 1, furthercomprising: prior to eroding the device state log: determining whether atime base of the multi-state device is different from a time base of thepower meter; and upon determining that the time base of the multi-statedevice is different from the time base of the power meter, aligning thedevice state log and the power trace to compensate for any timedeviations.
 4. The method of claim 1, wherein using the updated powermodel to estimate the energy consumption of the multi-state devicecomprises: determining, by the processing device, mean and peak valuesfor each power state in the eroded device state log; and creating, bythe processing device, an initial estimate of a state power trace basedupon the mean and peak values and the eroded device state log.
 5. Themethod of claim 4, wherein determining the mean and peak values for eachstate in the eroded device state log comprises calculating a mean andpeak value for the duration of time for each state transition in theeroded device state log based on the smoothed power trace.
 6. The methodof claim 4, wherein calculating the mean and peak values for each statein the eroded device state log comprises calculating a mean and peakvalue for each non-zero state in the eroded device state log based onthe smoothed power trace.
 7. The method of claim 4, wherein creating theinitial estimate of the state power trace comprises replacing each statevalue in the eroded power state log with a corresponding mean statepower value.
 8. The method of claim 1, wherein smoothing the power tracecomprises applying a moving average to filter the power trace.
 9. Adevice for updating a power model for a multi-state device, the devicecomprising: a power meter configured to measure power consumed by themulti-state device for a first period of time and generate a digitalrepresentation of a power trace based on the measured power consumption;a processor; and a non-transitory computer readable medium operablyconnected to the processor, the computer readable medium containing aset of instructions configured to instruct the processor to: receive adevice state log comprising a time-based representation of states of themulti-state device for the first period of time and the digitalrepresentation of the power trace generated by the power meter, erodethe device state log by setting to zero a value of the representationfor a duration of time of state transition at each state transitionwithin the device state log, thereby producing an eroded device statelog, smooth the power trace by applying a finite impulse response filterto the power trace, determine energy consumption based on an area underthe smoothed power trace for the first period of time in the erodeddevice state log, create an updated power model for the multi-statedevice based upon the energy consumption for the first period of time inthe eroded device state log, store the updated power model in anon-transitory computer readable medium operably connected to themulti-state device, and use the updated power model to estimate energyconsumption of the multi-state device.
 10. The device of claim 9,wherein the set of instructions further comprises instructionsconfigured to instruct the processor to replace the power model of thedevice with the updated power model.
 11. The device of claim 9, whereinthe set of instructions further comprises instructions configured toinstruct the processor to, prior to eroding the device state log:determine whether a time base of the multi-state device is differentfrom a time base of the power meter; and upon determining that the timebase of the multi-state device is different from the time base of thepower meter, align the device state log and the power trace tocompensate for any time deviations prior to eroding the device statelog.
 12. The device of claim 9, wherein the set of instructions forusing the updated power model to estimate the energy consumption of themulti-state device comprise instructions configured to instruct theprocessor to: determine mean and peak values for each power state in theeroded device state log; and create an initial estimate of a state powertrace based upon the mean and peak values and the eroded device statelog.
 13. The device of claim 12, wherein the set of instructions fordetermining the mean and peak values for each state in the eroded devicestate log further comprise instructions configured to instruct theprocessor to calculate a mean and peak value for the duration of timefor each state transition in the eroded device state log based on thesmoothed power trace.
 14. The device of claim 12, wherein the set ofinstructions for calculating the mean and peak values for each state inthe eroded device state log further comprise instructions configured toinstruct the processor to calculate a mean and peak value for eachnon-zero state in the eroded device state log based on the smoothedpower trace.
 15. The device of claim 12, wherein the set of instructionsfor creating the initial estimate of the state power trace furthercomprise instructions configured to instruct the processor to replaceeach state value in the eroded power state log with a corresponding meanstate power value.
 16. The device of claim 9, wherein the set ofinstructions for smoothing the power trace further comprise instructionsconfigured to instruct the processor to apply a moving average to filterthe power trace.
 17. A method of updating a power model for amultifunction printing device, the method comprising: receiving, at aprocessing device, a device state log comprising a time-basedrepresentation of states of the multifunction printing device for afirst period of time, wherein each of the states represents a specificfunction that the multifunction print device is configured to perform;measuring, by a power meter, power consumed by the multifunctionprinting device for the first period of time and generating a digitalrepresentation of a power trace based on the measured power consumption;receiving by the processing device, the digital representation of thepower trace; eroding, by the processing device, the device state log,wherein the eroding comprises setting to zero a value of therepresentation for a duration of time of state transition at each statetransition within the device state log, thereby producing an erodeddevice state log; smoothing, by the processing device, the power traceby applying a finite impulse response filter to the power trace;determining, by the processing device, energy consumption based on anarea under the smoothed power trace for the first period of time in theeroded device state log; creating, by the processing device, an updatedpower model for the multifunction print device based upon the energyconsumption for the first period of time in the eroded device state log;storing, by the processing device, the updated power model in anon-transitory computer readable medium operably connected to themultifunction printing device; and using the updated power model toestimate energy consumption of the multifunction printing device. 18.The method of claim 17, further comprising replacing the power model ofthe device with the updated power model.
 19. The method of claim 17,wherein using the updated power model to estimate the energy consumptionof the multifunction printing device comprises: determining, by theprocessing device, mean and peak values for each power state in theeroded device state log; and creating, by the processing device, aninitial estimate of a state power trace based upon the mean and peakvalues and the eroded device state log.
 20. The method of claim 19,wherein determining the mean and peak values for each state in theeroded device state log comprises calculating a mean and peak value forthe duration of time for each state transition in the eroded devicestate log based on the smoothed power trace.
 21. The method of claim 19,wherein calculating the mean and peak values for each state in theeroded device state log comprises calculating a mean and peak value foreach non-zero state in the eroded device state log based on the smoothedpower trace.
 22. The method of claim 19, wherein creating the initialestimate of the state power trace comprises replacing each state valuein the eroded power state log with a corresponding mean state powervalue.